Genetics Tenth

ICSE

1. Genetics Interesting and exciting - Jegatheeswari Karthik

2. Heredity- Like begets Like Transmission of genetically based characters from parents to offspring. (or) ‘The genetic constitution of an individual’. Young ones look like their parents. Cats produce ------- ? Guava seed germinate to------- ? Human give birth to -------- ? Bacteria in curd --------- ?

3. Like begets Like and yet there are variations Offspring's are never identical to their parents. Homo sapiens - S hare many common characteristics. Races or Tribes look different. Even with in family members. These small differences among the individuals of the same species are called variations.

4. Example In most people, the earlobe is hanging and is called a free earlobe. However, in some people, the earlobe is closely attached to the side of the head, and it is called an attached earlobe. Free ear lobe Attached ear lobe Blue and Brown eyes

5. Genetics - Some Basic Fundamentals Genetics - It is the study of transmission of characters from parents to offspring and the laws relating to such transmission. Heredity- The phenomenon of passing of characters from parents to progeny through successive generations is called heredity . Variation- The difference in the characters or traits among the individuals of a species is called variation .

6. Character and Traits Any inheritable feature of an organism is a CHARACTER The alternate forms of a character is called TRAITS Ear lobe is the character. Free or attached is the trait. Colour of the eye is the character. Blue or brown eyes is the trait.

7. Find out character and Traits Eye Brows - Heavy, brushy, Rh positive , Rh negative - Rh Blood type Pod colour - Yellow or Green

8. Chromosomes The chromosome is a thread-like structure in the nucleus of a cell. It is formed of DNA and carries the genes. The chromosome number is constant for the individuals of a species. For example, humans have 46 chromosomes.

9. Some more examples are given in the following table. Organism Number of Chromosomes Mouse 40 (20 pairs) Gorilla 48 Dog 78 Onion 16 Maize 20

10. Smallest number of chromosome Smallest number:  The female of a subspecies of the ant,  Myrmecia pilosula , has one pair of chromosomes per cell. Its male has only  one  chromosome in each cell.

11. Largest number of chromosome Largest number:  In the fern family of plants, the species  Ophioglossum reticulatum  has about 630 pairs of chromosomes, or  1260  chromosomes per cell.

12. Number of chromosomes in humans A pair of corresponding chromosomes of the same shape and size, one from each parent, is known as homologous chromosomes . Autosomes (22 pairs in humans) Sex Chromosomes (23rd pair of chromosomes in humans)

13. Allosomes in Humans There are two types of sex chromosomes— X chromosome and Y chromosome.

14. Male and Female A male has one X chromosome and one Y chromosome (XY). A female has both X chromosomes (XX).

15. Sex determination The process by which the sex of a person is determined is called sex determination . If a sperm carrying the X chromosome fertilizes an ovum( which always carries the X chromosome), then the combination of sex chromosomes will be XX, and hence, the child born will be a female (girl). If a sperm carrying the Y chromosome fertilizes an ovum, then the combination of sex chromosomes will be XY, and hence, the child born will be a male (boy).

16. Sex determination The type of sperm that fertilizes the egg determines whether the child will be male or female. Thus, the male ( Father ) is responsible for the sex of the baby.

17. Chromosomes , carriers of Gene Chromosomes carry genes, that are responsible for the characteristics of species. Lion and the Cat have the same number of Chromosomes- 38 Yet they are distinct from other This is because of genes.

18. Distinct characteristics Body size Appearance Colour Behaviour

19. Genes Wilhelm Johanssen - Geneticist – 1909 19,000 genes in Humans. Chromosome no. 1 has largest number of genes – 2968 Y Chromosome has fewest number of genes - 231

20. Genome A  genome  is an organism's complete set of DNA, including all of its genes. Each  genome  contains all of the information needed to build and maintain that organism. In humans, a copy of the entire  genome —more than 3 billion DNA base pairs—is contained in all cells that have a nucleus.

21. Allele Every gene has two alternative forms for a character producing different effects . These alternative forms are called alleles. Character Alternative forms Tongue rolling Rolling , Non-rolling

22. Allele

23. Allele

24. Alleles Alternate forms of a gene, occupying the same position (locus) on homologous chromosomes and affecting the same characteristic but in different ways. Homozygous - RR rr Heterozygous - Rr rR

25. Find out homozygous or Heterozygous GG gg Tt Gg

26. Dominant and Recessive alleles

27. Dominant and Recessive alleles Dominant and recessive traits exist when a trait has two different forms at the gene level. The trait that first appears or is visibly expressed in the organism is called the dominant trait. The trait that is present at the gene level but is masked and does not show itself in the organism is called the recessive trait.

28. Rolling and non- rolling R – Dominant r - Recessive RR rr Rr

29. Height of pea plant Tallness is dominant Dwarfness is recessive TT tt Tt

30. Colour of the flower PURPLE (Dominant) WHITE( Recessive) PP pp Pp

31. Colour of the flower Yellow Green

32. Homozygous and Heterozygous Homozygous – homo- similar- Zygos - Pair BB bb TT tt Heterozygous – hetero-different – zygos - pair Bb Tt

33. Tongue rolling The people will be having two options Rolling or Non- rolling There are three options of genes RR Rr rr Homozygous Heterozygous Homozygous dominant dominant recessive

34. Tallness of a plant Two options Tall or Dwarf Three option of genes TT Tt tt Homozygous Heterozygous Homozygous Dominant Dominant Recessive

35. Phenotype and Genotype Phenotype- The observable character that is genetically controlled. Eg. Height of a plant or Humans Genotype – The set of genes present in the cells of an organism. TT tt Tt

36. Example Mother - Roller Father - Roller Three kids – Two girls (One roller ) One boy(roller)

37. Both are tongue rollers( Both are homozygous dominant) Father Mother XY XX RR RR Meiosis X Y X X R R R R

38. Father Mother X Y X X X X (Girl) XX (Girl) YX (Boy) YX(Boy)

39. Both are tongue rollers Father Mother XY XX Rr Rr Meiosis X Y X X r R R r

40. Father Mother X Y X X X X(Girl) (Girl)XX YX (Boy) (Boy)YX r r r R r r

41. WHAT IS PEDIGREE CHART Chart that shows the presence or absence of a trait within a family across generations. WHY IS IT NECESSARY? Pedigrees  are used to analyze the pattern of inheritance of a particular trait throughout a family. Pedigrees show the presence or absence of a trait as it relates to the relationship among parents, offspring, and siblings.

42. Rules to create a pedigree chart (The family tree) Pedigrees represent family members and relationships using standardized symbols. By analyzing a pedigree, we can determine  genotypes , identify  phenotypes , and predict how a trait will be passed on in the future. The information from a pedigree makes it possible to determine how certain alleles are inherited: whether they are  dominant ,  recessive ,  autosomal , or  sex-linked .

43. Pedigree symbols

44. Any difference we want to show means hollow and solid

45. Example of inheritance Both father and mother are tongue rollers. Of their three children, two are tongue rollers and one cannot roll the tongue. The recessive allele ‘ rr ’ in the third child for non-rolling indicates that in ‘ rr ’ the child must have received one ‘r’ from each parent. Therefore, each parent is heterozygous for tongue rolling (Rr).

46. Draw a pedigree chart 1. In Family A, the parents had 5 children. Out of 5, 3 girls and two boys. Both the parents have free ear lobes out of 3 girls, two are having free ear lobes and the other one having attached ear lobe. Out of 2 boys one is having free ear lobe and the other is having attached ear lobe.

47. Draw a pedigree chart In Family B, the parents had 4 children. Out of 4, 2 girls and 2 boys. Both the parents have attached ear lobes All their kids also have attached ear lobes.

48. Punnet square is a simple table that shows all the possible combinations of alleles that can result when the two organisms cross. Father allele will be placed on one side Mother allele will be placed on one side Then the possible combinations are tried

49. Punnet square R R R R R R R R R R R R R

50. Punnet square R R r R r R R R r r R r r

51. Sex linked inheritance Sex-linked inheritance is the appearance of a trait which is due to the presence of an allele exclusively either on X chromosomes or on the Y chromosome. X-linked genetic disorders or X-linked inheritance There are certain disorders in humans due to heredity. They are Colour blindness Haemophilia

52. Colour Blindness Affected individuals cannot able to differentiate between colours. Mostly red and green More common in males than females. Defects are due to the recessive gene present on X chromosome.

53. Colour Blindness test

54. Haemophilia The person suffering from this defect are at the risk of bleeding to death because the blood fails to clot in them. Very rare. Haemophilic Males are found.

55. Case-2

56. Criss-cross Inheritance X-linked inheritance is also called criss-cross inheritance . This is because the son may inherit a trait from the normal carrier mother

57. Y-linked Inheritance Traits occur due to dominant genes which are on the Y chromosome. Such traits occur only in males. For example, hypertrichosis (hair growth on ears) and baldness.

58. Polydactyly

59. Mendel's experiments on inheritance

60. Deserving students Sanjana 8. Poorvi Vinutha 9. Bhargav Anushree 10. Tejaswi Shuchitha 11. Navitha Shreya Jyothi Charmika

61. Why Mendel selected Pea plant? Many varieties were available in alternative forms of a character .

62. Why Mendel selected Pea plant? Can be grown easily. Have shorter life span. Both male and female reproductive parts are present in the same flower. So self pollination will takes place. Artificial cross pollination is also possible. Varieties were available in pure forms.

63. Mono hybrid and dihybrid cross Mono hybrid cross –Crossing two plants by taking only one feature at a time. Di hybrid cross - Crossing two plants by taking two features together at a time.

64. Mono-Hybrid Cross

65. Monohybrid ratio

66. Examples Case 2 Round and wrinkled seeds Round is dominant Case 3 Terminal flowers and auxiliary flowers Auxiliary character is dominant

67. poorvi Bhat Jyothi Vinutha.V Charmika Sai sadhana Tejaswi Bhargav Anushree Deekshitha.P

68. Conclusions from the above results Each pair of a contrasting characters depends on a pair of genes. For example TT( TALL) Tt(HYBRID) tt (Dwarf). Each individual carries such genes in duplicate. (one from father and one from mother). Individual produces gametes which are haploid. (Either T or T in case of Tt) ( T or t in case of Tt) (t or t in case of tt ) Fertilisation of the gametes restores diploid condition. Sex cells with respect to genes they contain fertilised at random.

69. Dihybrid cross It is the cross between two plants that differ by two pairs of contrasting characters. Round and Yellow seeds ( RRYY) Wrinkled and green seeds ( rryy )

70. MALE FEMALE RY Ry rY ry RY RRYY RRYy RrYY RrYy Ry rY ry

71. Dihybrid ratio Round Yellow ; 9 Round green ; 3 Wrinkled yellow ; 3 9:3:3:1 Wrinkled green ; 1

72. Mendel's laws of inheritance Law of dominance Law of segregation Law of independent assortment

73. Law of dominance ‘ Out of a pair of contrasting characters present together, only one is able to express itself and the other remains supressed ’. ( Tt ) Hybrid One that expresses itself is Dominant character. ( T ) Tall The other that is unexpressed is the recessive . ( t ) Dwarf The recessive character express only when the pair consists only of homozygous recessive . ( tt )

74. Law of segregation( Law of purity of Gametes) The two members of a pair of factors separate during the formation of gametes. The gamete combine together by random fusion at the time of zygote formation.

75. Law of independent assortment When there are two pairs of characters, the distribution of the allele of one character into the gametes is independent of the distribution of the alleles of the other character. Round yellow seeds RRYY

76. Application of Mendel’s laws Gives an idea of new combination in the new generation. Enables to predict the frequency of characters in the new generation. Better quality plant and animal breeds can be produced. By the technique of hybridization, new type of plants with new combination of useful characters can be produced.

77. Mutation Mutation is the sudden change in one or more genes, or in the number or in the structure of chromosomes.

78. Sickle cell anaemia It a blood disease caused due to gene mutation. The mutation causes changes in DNA and results in the production of sickle-shaped RBCs.

79. Effects of sickle cell anaemia

80. Down’s Syndrome It is a mental deficiency caused due to one extra chromosome (chromosome no. 21). Down syndrome  or  Down's syndrome , also known as trisomy 21, is a genetic  disorder  caused by the presence of all or part of a third copy of chromosome 21. It is usually associated with physical growth delays, mild to moderate intellectual disability, and characteristic facial features.

81. Radioactive Radiations Radioactive radiations alter the gene structure. The atomic explosions which occurred during World War II in 1945 in Japan led to a number of deformities in the body of animals and plants.